Human mesenchymal stem/stromal cells (hMSCs), when engrafted into immunodeficient mice, can form ectopic bone organs with hematopoietic stem cell (HSC) supportive functions. However, the ability to do so, through a cartilage intermediate, appears limited to 30% of donor bone marrow samples. In this study, we characterize the heterogeneous nature of hMSCs and their ability to efficiently form humanized ossicles observed in “good donors” to correlate with the frequency and functionality of chondrocyte progenitors. Flow cytometry of putative hMSC markers was enriched in the CD271⁺CD51⁺ stromal cell subset, which also possessed enhanced hMSC activity as assessed by single-cell colony-forming unit fibroblast (CFU-F) and undifferentiated mesensphere formation. Transcriptome analysis of CD271⁺ cells presented upregulation of chondrogenesis-/osteogenesis-related genes and HSC/niche maintenance factors such as C-X-C motif chemokine 12 (CXCL12) and ANGIOPOIETIN 1. Among the candidate genes selected to enrich for subsets with greater chondrogenic ability, cells negative for the actin cross-linker PALLADIN displayed the greatest CFU-F potential. Our study contributes to a better characterization of ossicle-forming hMSCs and their efficient isolation for the optimized engineering of human bone organs.

中文翻译：

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CD271+CD51+PALLADIN- 人间充质基质细胞具有增强的小骨形成潜力

人间充质干细胞/基质细胞 (hMSCs) 移植到免疫缺陷小鼠体内后，可形成具有造血干细胞 (HSC) 支持功能的异位骨器官。然而，通过软骨中间体这样做的能力似乎仅限于 30% 的供体骨髓样本。在这项研究中，我们描述了 hMSCs 的异质性以及它们在“好供体”中观察到的有效形成人源化听小骨的能力，以与软骨细胞祖细胞的频率和功能相关。推定的 hMSC 标志物的流式细胞术富含 CD271 ⁺ CD51 ⁺基质细胞亚群，通过单细胞集落形成单位成纤维细胞 (CFU-F) 和未分化的间质形成评估，其也具有增强的 hMSC 活性。CD271 ⁺细胞的转录组分析显示了软骨形成/成骨相关基因和 HSC/生态位维持因子如 CXC 基序趋化因子 12 (CXCL12)和血管生成素 1的上调。在选择以富集具有更大软骨形成能力的亚群的候选基因中，肌动蛋白交联剂 PALLADIN 阴性的细胞显示出最大的 CFU-F 潜力。我们的研究有助于更好地表征小骨形成 hMSCs 及其有效分离，以优化人体骨骼器官的工程。